Semiconductor packages and methods of forming the same

ABSTRACT

Embodiments of the present disclosure include semiconductor packages and methods of forming the same. An embodiment is a semiconductor package including a first package including one or more dies, and a redistribution layer coupled to the one or more dies at a first side of the first package with a first set of bonding joints. The redistribution layer including more than one metal layer disposed in more than one passivation layer, the first set of bonding joints being directly coupled to at least one of the one or more metal layers, and a first set of connectors coupled to a second side of the redistribution layer, the second side being opposite the first side.

This application is a divisional application of U.S. patent applicationSer. No. 14/222,475, entitled “Semiconductor Packages and methods offorming the same,” filed on Mar. 21, 2014, which application isincorporated herein by reference.

BACKGROUND

Semiconductor devices are used in a variety of electronic applications,such as personal computers, cell phones, digital cameras, and otherelectronic equipment, as examples. Semiconductor devices are typicallyfabricated by sequentially depositing insulating or dielectric layers,conductive layers, and semiconductive layers of material over asemiconductor substrate, and patterning the various material layersusing lithography to form circuit components and elements thereon.

The semiconductor industry has experienced rapid growth due toimprovements in the integration density of a variety of electroniccomponents (e.g., transistors, diodes, resistors, capacitors, etc.). Forthe most part, this improvement in integration density has come fromshrinking the semiconductor process node (e.g., shrink the process nodetowards the sub-20 nm node). As the demand for miniaturization, higherspeed and greater bandwidth, as well as lower power consumption andlatency has grown recently, there has grown a need for smaller and morecreative packaging techniques of semiconductor dies.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A through 1D illustrate cross-sectional views of intermediatesteps in forming a die package in accordance with some embodiments.

FIGS. 2A through 2E illustrate cross-sectional views of intermediatesteps in forming a redistribution layer in accordance with someembodiments.

FIGS. 3A through 3D illustrate cross-sectional views of intermediatesteps in forming a semiconductor package including the die package fromFIGS. 1A through 1D and the redistribution layer from FIGS. 2A through2E in accordance with some embodiments.

FIGS. 4A through 4D illustrate a bonding interface between the diepackage from FIGS. 1A through 1D and the redistribution layer from FIGS.2A through 2E in accordance with various embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments will be described with respect to embodiments in a specificcontext, namely a three dimensional (3D) integrated fan-out (InFO)package-on-package (PoP) device. Other embodiments may also be applied,however, to other electrically connected components, including, but notlimited to, package-on-package assemblies, die-to-die assemblies,wafer-to-wafer assemblies, die-to-substrate assemblies, in assemblingpackaging, in processing substrates, interposers, substrates, or thelike, or mounting input components, boards, dies or other components, orfor connection packaging or mounting combinations of any type ofintegrated circuit or electrical component.

FIGS. 1A through 1D illustrate cross-sectional views of intermediatesteps in forming a die package 100 in accordance with some embodiments.The die package 100 in FIG. 1A includes dielectric layer 104 over acarrier substrate 102, and bond pads 106 and electrical connectors 108over the dielectric layer 104. The carrier substrate 102 may be anysuitable substrate that provides (during intermediary operations of thefabrication process) mechanical support for the layers over the carriersubstrate 102. The carrier substrate 102 may be a wafer including glass,silicon (e.g., a silicon wafer), silicon oxide, metal plate, a ceramicmaterial, or the like.

The dielectric layer 104 is formed over the carrier substrate 102. Thepassivation layer can be silicon nitride, silicon carbide, siliconoxide, low-k dielectrics such as carbon doped oxides, extremely low-kdielectrics such as porous carbon doped silicon dioxide, a polymer, suchas an epoxy, polyimide, benzocyclobutene (BCB), polybenzoxazole (PBO),the like, or a combination thereof, although other relatively soft,often organic, dielectric materials can also be used. The dielectriclayer 104 may be deposited by chemical vapor deposition (CVD), physicalvapor deposition (PVD), atomic layer deposition (ALD), aspin-on-dielectric process, the like, or a combination thereof.

The bond pads 106 are formed over the dielectric layer 104. In someembodiments, the bond pads 106 are formed by forming recesses (notshown) into the dielectric layer 104. The recesses may be formed toallow the bond pads 106 to be embedded into the dielectric layer 104. Inother embodiments, the recesses are omitted as the bond pads 106 may beformed on a first side 104A of the dielectric layer 104. The bond pads106 electrically and/or physically couple the subsequently bonded dies110 to the subsequently bonded package 400 (see FIG. 3D), and/or theelectrical connectors 108. In some embodiments, the bond pads 106include a thin seed layer (not shown) made of copper, titanium, nickel,gold, the like, or a combination thereof. The conductive material of thebond pads 106 may be deposited over the thin seed layer. The conductivematerial may be formed by an electro-chemical plating process, CVD, ALD,PVD, the like, or a combination thereof. In an embodiment, theconductive material of the bond pads 106 is copper, tungsten, aluminum,silver, gold, the like, or a combination thereof.

In an embodiment, the bond pads 106 are underbump metallizations (UBMs)that include three layers of conductive materials, such as a layer oftitanium, a layer of copper, and a layer of nickel. However, one ofordinary skill in the art will recognize that there are many suitablearrangements of materials and layers, such as an arrangement ofchrome/chrome-copper alloy/copper/gold, an arrangement oftitanium/titanium tungsten/copper, or an arrangement ofcopper/nickel/gold, that are suitable for the formation of the UBMs 106.Any suitable materials or layers of material that may be used for theUBMs 106 are fully intended to be included within the scope of thecurrent application.

The electrical connectors 108 are formed over the dielectric layer 104and extend from the dielectric layer 104 in a direction that issubstantially perpendicular to the first side 104A of the dielectriclayer 104. The electrical connectors 108 may be stud bumps, which areformed by wire bonding on the bond pads, and cutting the bond wire witha portion of bond wire left attached to the respective bond ball. Forexample, in FIG. 1A, the electrical connectors 108 include a lowerportion and an upper portion, wherein the lower portion may be a bondball formed in the wire bonding, and the upper portion may be theremaining bond wire. The upper portion of the electrical connector 108may have a uniform width and a uniform shape that are uniform throughoutthe top part, the middle part, and the bottom part of upper portion. Theelectrical connectors 108 are formed of non-solder metallic materialsthat can be bonded by a wire bonder. In some embodiments, the electricalconnectors 108 are made of copper wire, gold wire, the like, or acombination thereof, and may have a composite structure including aplurality of layers.

In alternative embodiments, the electrical connectors 108 are formedthrough electrical plating. In these embodiments, the electricalconnectors 108 are made of copper, aluminum, nickel, gold, silver,palladium, the like, or a combination thereof, and may have a compositestructure including a plurality of layers. In these embodiments, asacrificial layer (not shown) is formed over the carrier substrate. Aplurality of openings is formed in the sacrificial layer to expose theunderlying bond pads. A plating step is then performed to plate theelectrical connectors 108. After the formation of the electricalconnectors 108, the sacrificial layer is then removed.

The electrical connectors 108 and the bond pads 106 may be collectivelyreferred to as a backside redistribution layer for the die package 100.This backside redistribution layer may be used to couple anotherpackage(s) or component(s) (see package 400 in FIG. 3D) to the diepackage 100.

FIG. 1B illustrates bonding one or more dies 110 to the bond pads 106. Afirst side of the die(s) 110 may be coupled to the bond pads 106. Thedie(s) 110 may be a single die or may be more than two dies. The dies(s)110 may include a logic die, such as a central processing unit (CPU), agraphics processing unit (GPU), the like, or a combination thereof. Insome embodiments, the die(s) 110 includes a die stack (not shown) whichmay include both logic dies and memory dies. The die(s) 110 may includean input/output (I/O) die, such as a wide I/O die that provides aconnection between the die package 100 and the subsequently attachedpackage 400 (see FIG. 3D).

The die(s) 110 include contact areas 112 on a second side of the die(s)110. In some embodiments, the contact areas 112 are similar to the bondpads 106 described above and the description is not repeated herein. Inother embodiments, the contact areas 112 are vias extending from thesecond side of the die(s) partially into the die(s) 110 or, in someembodiments, completely through the die(s) 110. The vias 112 may beformed by an etch process to form holes (not shown) in the die(s) 110and the holes may be filled by a conductive material such as copper,aluminum, nickel, gold, silver, palladium, the like, or a combinationthereof, and may have a composite structure including a plurality oflayers. The vias 112 may also include seed layers, barrier layers,liners, the like, or a combination thereof.

FIG. 1C illustrates the encapsulation of the die(s) 110 and theelectrical connectors 108. In some embodiments, the die(s) 110 and theelectrical connectors 108 are encapsulated by a molding material 114.The molding material 114 may be molded on the die(s) 110 and theelectrical connectors 108, for example, using compression molding. Insome embodiments, the molding material 114 is made of a moldingcompound, a polymer, an epoxy, silicon oxide filler material, the like,or a combination thereof. A curing step may be performed to cure themolding material 114, wherein the curing may be a thermal curing, aUltra-Violet (UV) curing, the like, or a combination thereof.

In some embodiments, the die(s) 110, the contact areas 112, and theelectrical connectors 108 are buried in the molding material 114, andafter the curing of the molding material 114, a planarization step, suchas a grinding, is performed on the molding material 114 as illustratedin FIG. 1D. The planarization step is used to remove excess portions ofthe molding material 114, which excess portions are over top surfaces ofthe contact areas 112 and the electrical connectors 108. In someembodiments, surfaces 112A of the contact areas 112 and surfaces 108A ofthe electrical connectors 108 are exposed, and are level with a surface114A of the molding material 114. The electrical connectors 108 may bereferred to as through molding vias (TMVs), through package vias (TPVs),and/or through InFO vias (TIVs) and will be referred to as TIVs 108hereinafter.

FIGS. 2A through 2E illustrate cross-sectional views of intermediatesteps in forming a redistribution layer 204 in accordance with someembodiments. FIG. 2A illustrates a redistribution layer 204 over acarrier substrate 202. The redistribution layer 204 is formed with afirst side 204A distal the carrier substrate 202 and a second side 204Bproximate the carrier substrate 202.

The redistribution layer 204 includes more than one metal layer, namelyM₁ and M_(N), wherein the metal layer M₁ is the metal layer immediatelyadjacent the carrier substrate 202, and metal layer M_(N) (sometimesreferred to as the top metal layer M_(N)) is the metal layer immediatelyadjacent UBMs 210 (see FIG. 2B). Throughout the description, the term“metal layer” refers to the collection of the metal lines 208 in thesame layer. The redistribution layer 204 further includes more than onepassivation layer 206, wherein the more than one metal layers (M₁through M_(N)) are disposed in the more than one passivation layers 206.

The passivation layers 206 can be silicon nitride, silicon carbide,silicon oxide, low-k dielectrics such as carbon doped oxides, extremelylow-k dielectrics such as porous carbon doped silicon dioxide, apolymer, such as an epoxy, polyimide, BCB, PBO, the like, or acombination thereof, although other relatively soft, often organic,dielectric materials can also be used, and deposited by CVD, PVD, ALD, aspin-on-dielectric process, the like, or a combination thereof. In anembodiment, each passivation layer 206 is formed to a thickness fromabout 5 μm to about 15 μm. The passivation layers 206 may undergo acuring step to cure the passivation layers 206, wherein the curing maybe a thermal curing, an UV curing, the like, or a combination thereof.

The metal layers, M₁ and M_(N), may be formed using a single and/or adual damascene process, a via-first process, or a metal-first process.The metal layers (M₁ and M_(N)) and vias may be formed of a conductivematerial, such as copper, aluminum, titanium, the like, or a combinationthereof, with or without a barrier layer. In an embodiment, each of themetal layers M₁ through M_(N) has a thickness in a range from about 3 μmto about 15 μm.

A damascene process is the formation of a patterned layer embedded inanother layer such that the top surfaces of the two layers are coplanar.A damascene process, which creates either only trenches or vias, isknown as a single damascene process. A damascene process, which createsboth trenches and vias at once, is known as a dual damascene process.

In an exemplary embodiment, the metal layers M₁ through M_(N) are formedusing a dual damascene process. In this example, the formation of the M₁layer may begin with the formation of an etch stop layer (not shown) onthe lowermost passivation layer 206 and with the next passivation layer206 on the etch stop layer. Once the next passivation layer 206 isdeposited, portions of the next passivation layer 206 may be etched awayto form recessed features, such as trenches and vias, which can befilled with conductive material to connect different regions of theredistribution layer 204 and accommodate the metal lines 208 and vias.This process may be repeated for the remaining metal layers throughM_(N).

The redistribution layer 204 may be referred to as a frontsideredistribution layer for the die package 100. This frontsideredistribution layer 204 may be utilized to couple the die package 100via the connectors 212 to one or more packages, package substrates,components, the like, or a combination thereof.

The number of metal layers M₁ to M_(N) and the number of passivationlayers 206 are only for illustrative purposes and are not limiting.There could be other number of layers that is more or less than the twometal layers illustrated. There may be other number of passivationlayers, and other number of metal layers different from thoseillustrated in FIG. 2A.

FIG. 2B illustrates the forming of UBMs 210 over and electricallycoupled to the top metal layer M_(N). A set of openings (not shown) maybe formed through the topmost passivation layer 206 to expose surfacesof the metal lines 208 in the metal layer M_(N). The UBMs 210 may extendthrough these openings in the passivation layer 206 and also extendalong a surface of passivation layer 206. The UBMs 210 may include threelayers of conductive materials, such as a layer of titanium, a layer ofcopper, and a layer of nickel. However, one of ordinary skill in the artwill recognize that there are many suitable arrangements of materialsand layers, such as an arrangement of chrome/chrome-copperalloy/copper/gold, an arrangement of titanium/titanium tungsten/copper,or an arrangement of copper/nickel/gold, that are suitable for theformation of the UBMs 210. Any suitable materials or layers of materialthat may be used for the UBMs 210 are fully intended to be includedwithin the scope of the current application.

FIG. 2C illustrates the formation of a set of conductive connectors 212over and electrically coupled to the UBMs 210. The conductive connectors212 may be solder balls, metal pillars, controlled collapse chipconnection (C4) bumps, micro bumps, electroless nickel-electrolesspalladium-immersion gold technique (ENEPIG) formed bumps, or the like.The conductive connectors 212 may include a conductive material such assolder, copper, aluminum, gold, nickel, silver, palladium, tin, thelike, or a combination thereof. In an embodiment in which the conductiveconnectors 212 are solder bumps, the conductive connectors 212 areformed by initially forming a layer of solder through such commonly usedmethods such as evaporation, electroplating, printing, solder transfer,ball placement, or the like. Once a layer of solder has been formed onthe structure, a reflow may be performed in order to shape the materialinto the desired bump shapes. In another embodiment, the conductiveconnectors 212 are metal pillars (such as a copper pillar) formed by asputtering, printing, electro plating, electroless plating, CVD, or thelike. The metal pillars may be solder free and have substantiallyvertical sidewalls. In some embodiments, a metal cap layer (not shown)is formed on the top of the metal pillar connectors 212. The metal caplayer may include nickel, tin, tin-lead, gold, silver, palladium,indium, nickel-palladium-gold, nickel-gold, the like, or a combinationthereof and may be formed by a plating process.

FIG. 2D illustrates flipping the redistribution layer 204 over andplacing it on a dicing tape 218 and removing the carrier substrate 202.After the carrier substrate 202 is removed, the second side 204B of theredistribution layer 204 is exposed. As illustrated in FIG. 2D, a set ofopenings 220 are formed in at least one of the passivation layers 206 toexpose portions of the metal lines 208. The openings 220 may be formed alaser drill process, an etch process, the like, or a combinationthereof.

FIG. 2E illustrates the formation of a set of bonding structures 222 inthe openings 220 and electrically coupled to the exposed metal lines 208of the redistribution layer 204. The bonding structures 222 may includesolder paste, micro bumps, solder balls, UBMs, flux, the like, or acombination thereof. The details of the bonding structures will bediscussed below in FIGS. 4A through 4D.

FIGS. 3A through 3D illustrate cross-sectional views of intermediatesteps in forming a semiconductor package 300 including the die package100 from FIGS. 1A through 1D and the redistribution layer 204 from FIGS.2A through 2E in accordance with some embodiments.

FIG. 3A illustrates the die package 100 being flipped over with thecontact areas 112 and the TIVs 108 being over aligned with the bondingstructures 222 of the redistribution layer 204. FIG. 3B illustratesbonding the die package 100 to the redistribution layer 204.

The bonding between the die package 100 and the redistribution layer 204may be a solder bonding or a direct metal-to-metal (such as acopper-to-copper or tin-to-tin) bonding. In an embodiment, the diepackage 100 is bonded to the redistribution layer 204 by a reflowprocess. During this reflow process, the bonding structures 222 are incontact with the contact areas 112 and the TIVs 108 to physically andelectrically couple the die package 100 to the redistribution layer 204and to form bonding joints 224 from the bonding structures 222. In someembodiments, a bonding structure (not shown), which may be similar tothe bonding structures 222, is formed on the contact areas 112 and theTIVs 108 before the die package 100 and the redistribution layer 204 arebonded together.

In some embodiments, after the bonding process there may be a small gapbetween the die package 100 and the redistribution layer 204 caused bythe standoff height of the bonding structures 224. In other embodiments,there may be no gap between the die package 100 and the redistributionlayer 204.

Typically, the redistribution layer would be formed directly on the diepackage and the processes involved in forming the redistribution layer(e.g. passivation etching, passivation curing, metal line deposition,etc.) can cause significant warpage. However, in the disclosedembodiments, by forming the redistribution layer 204 on a carriersubstrate 202, and bonding the formed redistribution layer 204 to thedie package 100, the warpage of the package 300 can be reduced. Forexample, the carrier substrate 202 can be selected such that it is veryrigid and will have very minimal to no warpage during the formation ofthe redistribution layer 204. In addition, a carrier substrate 202 canbe selected such that it has a similar coefficient of thermal expansion(CTE) to the redistribution layer 204 and, will thus, minimize thewarpage from any CTE mismatch.

FIG. 3C illustrates removing the carrier substrate 102 to expose asecond side 104B of the dielectric layer 104. After the carriersubstrate 102 is removed, openings 302 are formed from the second side104B of the dielectric layer 104 to expose surfaces 108B of the TIVs 108and surfaces 106B of the bond pads 106. The openings 220 may be formed alaser drill process, an etch process, the like, or a combinationthereof.

FIG. 3D illustrates bonding a package 400 to the package 300 with a setof connectors 408 extending through the openings 302. The package 400includes a substrate 402 and one or more stacked dies 410 coupled to thesubstrate 402.

The substrate 402 may be made of a semiconductor material such assilicon, germanium, diamond, or the like. Alternatively, compoundmaterials such as silicon germanium, silicon carbide, gallium arsenic,indium arsenide, indium phosphide, silicon germanium carbide, galliumarsenic phosphide, gallium indium phosphide, combinations of these, andthe like, may also be used. Additionally, the substrate 402 may be asilicon-on-insulator (SOI) substrate. Generally, an SOI substrateincludes a layer of a semiconductor material such as epitaxial silicon,germanium, silicon germanium, SOI, silicon germanium on insulator(SGOI), or combinations thereof. The substrate 402 is, in onealternative embodiment, based on an insulating core such as a fiberglassreinforced resin core. One example core material is fiberglass resinsuch as FR4. Alternatives for the core material includebismaleimide-triazine (BT) resin, or alternatively, other PC boardmaterials or films. Build up films such as Ajinomoto build-up film (ABF)or other laminates may be used for substrate 402. The substrate 402 maybe referred to as a package substrate 402.

The substrate 402 may include active and passive devices (not shown inFIG. 3D). As one of ordinary skill in the art will recognize, a widevariety of devices such as transistors, capacitors, resistors,combinations of these, and the like may be used to generate thestructural and functional requirements of the design for thesemiconductor package 400. The devices may be formed using any suitablemethods.

The substrate 402 may also include metallization layers (not shown). Themetallization layers may be formed over the active and passive devicesand are designed to connect the various devices to form functionalcircuitry. The metallization layers may be formed of alternating layersof dielectric (e.g., low-k dielectric material) and conductive material(e.g., copper) with vias interconnecting the layers of conductivematerial and may be formed through any suitable process (such asdeposition, damascene, dual damascene, or the like). In someembodiments, the substrate 402 is substantially free of active andpassive devices.

The substrate 402 may have bond pads 404 on a first side the substrate402 to couple to the stacked dies 410, and bond pads 406 on a secondside of the substrate 402, the second side being opposite the first sideof the substrate 402, to couple to the conductive connectors 408. Thebond pads 404 and 406 may be similar to the bond pads 106 describedabove and the description is not repeated herein, although the bond pads404, 406, and 106 need not be the same.

In the illustrated embodiment, the stacked dies 410 are coupled to thesubstrate 402 by with contact pads 414 and wire bonds 412, althoughother connections may be used, such as conductive bumps. In anembodiment, the stacked dies 410 are stacked memory dies. For example,the stacked memory dies 410 may include low-power (LP) double data rate(DDR) memory modules, such as LPDDR1, LPDDR2, LPDDR3, or the like memorymodules.

In some embodiments, the stacked dies 410 and the wire bonds 412 may beencapsulated by a molding material 414. The molding material 414 may bemolded on the stacked dies 410 and the wire bonds 412, for example,using compression molding. In some embodiments, the molding material 414is a molding compound, a polymer, an epoxy, silicon oxide fillermaterial, the like, or a combination thereof. A curing step may beperformed to cure the molding material 414, wherein the curing may be athermal curing, a UV curing, the like, or a combination thereof.

In some embodiments, the stacked dies 410 and the wire bonds 412 areburied in the molding material 414, and after the curing of the moldingmaterial 414, a planarization step, such as a grinding, is performed toremove excess portions of the molding material 414 and provide asubstantially planar surface for the package 400.

After the package 400 is formed, the package 400 is bonded to package300 by way of conductive connectors 408, the bond pads 406, the bondpads 106, and the TIVs 108. In some embodiments, the stacked memory dies410 may be coupled to the die(s) 110 through the contact pads 414, thewire bonds 412, the bond pads 406 and 404, the conductive connectors408, the bond pads 106, and the TIVs 108.

The conductive connectors 408 may be similar to the conductiveconnectors 212 described above and the description is not repeatedherein, although the conductive connectors 408 and 212 need not be thesame.

The bonding between the package 400 and the package 300 may be a solderbonding or a direct metal-to-metal (such as a copper-to-copper ortin-to-tin) bonding. In an embodiment, the package 400 is bonded to thepackage 300 by a reflow process. During this reflow process, theconductive connectors 408 are in contact with the bond pads 406 and 106,and the TIVs 108 to physically and electrically couple the package 400to the package 300.

An underfill material (not shown) may be injected or otherwise formed inthe space between the package 400 and the package 300 and surroundingthe conductive connectors 408. The underfill material may, for example,be a liquid epoxy, deformable gel, silicon rubber, or the like, that isdispensed between the structures, and then cured to harden. Thisunderfill material is used, among other things, to reduce damage to andto protect the conductive connectors 408.

It should be noted that the number of semiconductor dies (e.g.,semiconductor die(s) 110 and 410), through InFO vias (e.g., TIVs 108),and conductive connectors (e.g. conductive connectors 212 and 408) shownin FIG. 3D are merely an example. There may be many variations,modifications, and alternatives. For example, a person skilled in theart will recognize that the semiconductor package 500 may accommodateany number of semiconductor dies, TIVs, and conductive connectors.

FIGS. 4A through 4D illustrate a bonding interface between the diepackage 100 and the redistribution layer 204 in accordance with variousembodiments. The portion of package 500 that is illustrated in FIGS. 4Athrough 4D is the highlighted area of FIG. 3D that is labeled FIG. 4.The bonding structures 600 (e.g. 600A and 600B) in FIGS. 4A through 4Dare various embodiments of the bonding structure 222 as illustrated inFIG. 3A before the die package 100 and the redistribution layer 204 arebonded together.

FIG. 4A illustrates the bonding structures 600 of the die package 100and the redistribution layer 204 wherein the bonding structures 600 aremicro bumps. The bonding structures 600A are coupled to the bond pads106 and the TIVs 108 of the die package 100, and the bonding structures600B are coupled to the metal lines 208 of redistribution layer 204 inthe openings 220 (see FIG. 2D). In an embodiment, the bonding structures600A and 600B are formed to have a height H₁ in a range from about 10 μmto about 40 μm, and a width W₂ in a range from about 5 μm to about 50μm. The bonding structures 600A and 600B can be formed at a pitch P₁ ina range from about 10 μm to about 300 μm.

In the illustrated embodiment, both the bonding structures 600A and 600Bare micro bumps including seed layers 602 (602A and 602B), conductivelayers 604 (604A and 604B), and cap layers 606 (606A and 606B). Thebonding structures 600B coupled to the redistribution layer 204 areformed in the openings 220 (see FIG. 2D), with a portion of apassivation layer 206 separating the two openings 220 illustrated inFIG. 4A. In an embodiment, the openings 220 are formed to have a widthW₁ in a range from about 25 μm to about 150 μm.

The seed layers 602 may be formed by an electro-chemical platingprocess, CVD, ALD, PVD, the like, or a combination thereof. The seedlayer 602 may be formed of titanium copper alloy, tantalum copper alloy,the like, or a combination thereof.

The conductive layers 604 may be formed on the seed layer 602 by anelectro-chemical plating process, CVD, ALD, PVD, the like, or acombination thereof. The conductive layer 604 may be formed of copper,titanium, nickel, gold, the like, or a combination thereof to have athickness T₁ from about 2 μm to about 10 μm.

The cap layers 606 may be formed on the conductive layer 604 by anelectro-chemical plating process, CVD, ALD, PVD, the like, or acombination thereof. The cap layer 606 may be formed of tin, nickel,tin-lead, gold, silver, palladium, indium, nickel-palladium-gold,nickel-gold, the like, or a combination thereof to have a thickness T₂from about 3 μm to about 10 μm.

The bonding structures 600A are bonded to the bonding structures 600B bya reflow process. During this reflow process, at least the cap layers606A of the bonding structures 600A are in contact with at least the caplayers 606B of the bonding structures 600B to physically andelectrically couple the die package 100 to the redistribution layer 204and to form bonding joints 224 from the bonding structures 600A and600B.

FIG. 4B illustrates the bonding structures 600 of the die package 100and the redistribution layer 204 wherein the bonding structures 600 aremicro bumps with a metal paste layer 608. The bonding structures 600Aare coupled to the bond pads 106 and the TIVs 108 of the die package100, and the bonding structures 600B are coupled to the metal lines 208of redistribution layer 204 in the openings 220 (see FIG. 2D). In anembodiment, the bonding structures 600A and 600B are formed to have aheight H₁ in a range from about 50 μm to about 120 μm, and a width W₂ ina range from about 70 μm to about 250 μm. The bonding structures 600Aand 600B can be formed at a pitch P₁ in a range from about 140 μm toabout 400 μm.

In the illustrated embodiment, both the bonding structures 600A and 600Bare micro bumps including seed layers 602 (602A and 602B), conductivelayers 604 (604A and 604B), cap layers 606 (606A and 606B), and metalpaste layers 608 (608A and 608B). The bonding structures 600B coupled tothe redistribution layer 204 are formed in the openings 220 (see FIG.2D), with a portion of a passivation layer 206 separating the twoopenings 220 illustrated in FIG. 4B. In an embodiment, the openings 220are formed to have a width W₁ in a range from about 90 μm to about 400μm.

The seed layers 602, the conductive layers 604, and the cap layers 606are similar to the description above in FIG. 4A and the descriptions arenot repeated herein.

The metal paste layers 608 may be formed on the cap layers 606 by ametal-paste printing process that is applied to the cap layers 606.According to the locations of the cap layers 606, a stencil may beemployed to print the metal paste on top of the cap layers 606. In someembodiments, the metal paste layers 608 are formed in openings of apatterned photo resist (not shown), which is removed after the openingsare filled with metal paste. The metal paste layers 608 may be formed ofa solder paste, a tin silver paste, flux, the like, or a combinationthereof to have a thickness T₃ in a range from about 30 μm to about 100μm.

The bonding structures 600A are bonded to the bonding structures 600B bya reflow process. During this reflow process, at least the metal pastelayers 608A of the bonding structures 600A are in contact with at leastthe metal paste layers 608B of the bonding structures 600B to physicallyand electrically couple the die package 100 to the redistribution layer204 and to form bonding joints 224 from the bonding structures 600A and600B.

The bonding structures 600 including the metal paste layers 608 mayimprove the quality of the bonding joint 224, but the bonding joints 224formed from the bonding structures 600 including the metal paste layers608 may also have an increased height and width.

FIG. 4C illustrates the bonding structures 600 of the die package 100and the redistribution layer 204 wherein the bonding structures 600 areformed of a metal paste layer. The bonding structures 600A are coupledto the bond pads 106 and the TIVs 108 of the die package 100, and thebonding structures 600B are coupled to the metal lines 208 ofredistribution layer 204 in the openings 220 (see FIG. 2D). In anembodiment, the bonding structures 600A and 600B are formed to have aheight H₁ in a range from about 30 μm to about 100 μm, and a width W₂ ina range from about 70 μm to about 250 μm. The bonding structures 600Aand 600B can be formed at a pitch P₁ in a range from about 140 μm toabout 400 μm.

In the illustrated embodiment, both the bonding structures 600A and 600Bare metal paste layers 612 (612A and 612B). The bonding structures 600Bcoupled to the redistribution layer 204 are formed in the openings 220(see FIG. 2D), with a portion of a passivation layer 206 separating thetwo openings 220 illustrated in FIG. 4C. In an embodiment, the openings220 are formed to have a width W₁ in a range from about 90 μm to about400 μm.

The metal paste layers 612 may be formed by a metal-paste printingprocess that is applied to the TIVs 108, the contact areas 112, and/orthe metal lines 208. According to the locations of the TIVs 108, thecontact areas 112, and/or the metal lines 208, a stencil may be employedto print the metal paste on top of the TIVs 108, the contact areas 112,and/or the metal lines 208. In some embodiments, the metal paste layers612 are formed in openings of a patterned photo resist (not shown),which is removed after the openings are filled with metal paste. Themetal paste layers 612 may be formed of a solder paste, a tin silverpaste, flux, the like, or a combination thereof to have the height H₁.

The bonding structures 600A are bonded to the bonding structures 600B bya reflow process. During this reflow process, at least the metal pastelayers 612A of the bonding structures 600A are in contact with at leastthe metal paste layers 612B of the bonding structures 600B to physicallyand electrically couple the die package 100 to the redistribution layer204 and to form bonding joints 224 from the bonding structures 600A and600B.

FIG. 4D illustrates the bonding structures 600 of the die package 100and the redistribution layer 204 wherein the bonding structures 600 areformed of solder bumps. The bonding structures 600A are coupled to thebond pads 106 and the TIVs 108 of the die package 100 and flux 620 isformed in the openings 220 of the redistribution layer 204 (see FIG.2D). In an embodiment, the bonding structures 600A are formed to have aheight H₁ in a range from about 20 μm to about 50 μm, and a width W₂ ina range from about 40 μm to about 80 μm. The bonding structures 600A canbe formed at a pitch P₁ in a range from about 80 μm to about 160 μm.

In the illustrated embodiment, the bonding structures 600A are bumpstructures including UBMs 630 and solder bumps 632 over the UBMs 630.The flux layers 620 are formed in the openings 220 of the redistributionlayer 204 (see FIG. 2D), with a portion of a passivation layer 206separating the two openings 220 illustrated in FIG. 4D. In anembodiment, the openings 220 are formed to have a width W₁ in a rangefrom about 25 μm to about 150 μm.

The UBMs 630 may be similar to the UBMs 210 described above and thedescription is not repeated herein. The solder bumps 632 may be similarto the connectors 212 described above and the description is notrepeated herein. In some embodiments, a layer of flux (not shown) may beformed on the contact areas 112 and the TIVs 108 before the solder bumps632 are formed. The flux layers 620 are formed in the openings 220, and,in some embodiments, the flux layers 620 substantially fill the openings220.

The bonding structures 600A are bonded to the flux layers 620 by areflow process. During this reflow process, at least the solder bumps632 of the bonding structures 600A are in contact with at least the fluxlayers 620 to physically and electrically couple the die package 100 tothe redistribution layer 204 and to form bonding joints 224 from thebonding structures 600A and the flux layers 620.

By forming the redistribution layer on a carrier substrate, and bondingthe formed redistribution layer on the die package, the warpage of thebonded package can be significantly reduced. Typically, theredistribution layer would be formed directly on the die package and theprocesses involved in forming the redistribution layer (e.g. passivationetching, passivation curing, metal line deposition, etc.) can causesignificant warpage. However, in the disclosed embodiments, the carriersubstrate for the redistribution layer can be selected such that it isvery rigid and will have very minimal to no warpage during the formationof the redistribution layer. In addition, the carrier substrate for theredistribution layer can be selected such that it has a similarcoefficient of thermal expansion (CTE) to the redistribution layer and,will thus, minimize any warpage from CTE mismatch.

An embodiment is a semiconductor package including a first packageincluding one or more dies, and a redistribution layer coupled to theone or more dies at a first side of the first package with a first setof bonding joints. The redistribution layer including more than onemetal layer disposed in more than one passivation layer, the first setof bonding joints being directly coupled to at least one of the one ormore metal layers, and a first set of connectors coupled to a secondside of the redistribution layer, the second side being opposite thefirst side.

Another embodiment is a semiconductor package including a die packageincluding a first die having a first side and a second side, the secondside being opposite the first side, an encapsulant surrounding the firstdie and having a first side substantially level with the first side ofthe first die and a second side substantially level with the second sideof the first die, and a through package via extending through theencapsulant from the first side to the second side of the encapsulant.The semiconductor package further includes a redistribution layer bondedto the first side of the first die and the through package via with aset of bonding joints, the redistribution layer comprising a pluralityof metal layers disposed in a plurality of passivation layers, each ofthe set of bonding joints being directly coupled to a first metal layerof the plurality of metal layers.

A further embodiment is a method including forming a first die packageover a first carrier substrate, the first die package comprising a firstdie and a first electrical connector, forming redistribution layer overa second carrier substrate, the redistribution layer including one ormore metal layers disposed in one or more passivation layers, andremoving the second carrier substrate from the redistribution layer toexpose a first passivation layer of the one or more passivation layers.The method further includes forming openings in the first passivationlayer to expose portions of a first metal layer of the one or more metallayers, forming a first set of bonding structures in the openings in thefirst passivation layer, the first set of bonding structures beingcoupled to the first metal layer, and bonding the redistribution layerto the first die package using the first set of bonding structures toform a first set of bonding joints, at least one of the first set ofbonding joints being bonded to the first die of the first die packageand at least another one of the first set of bonding joints being bondedto the first electrical connector.

In yet another embodiment, a method is provided. The method includesforming a first die package over a first carrier substrate, the firstdie package including a first die and a first electrical connector,forming redistribution layer over a second carrier substrate, theredistribution layer including one or more metal layers disposed in oneor more passivation layers, and removing the second carrier substratefrom the redistribution layer to expose a first passivation layer of theone or more passivation layers. The method further includes formingopenings in the first passivation layer to expose portions of a firstmetal layer of the one or more metal layers, and forming a first set ofbonding structures in the openings in the first passivation layer, thefirst set of bonding structures being coupled to the first metal layer.The redistribution layer is bonded to the first die package using thefirst set of bonding structures to form a first set of bonding joints,at least one of the first set of bonding joints being bonded to thefirst die of the first die package and at least another one of the firstset of bonding joints being bonded to the first electrical connector.

In yet still another embodiment, a method is provided. The methodincludes forming redistribution layer over a first carrier substrate,the redistribution layer including one or more metal layers disposed inone or more passivation layers, and after forming the redistributionlayer, attaching the redistribution layer to a second carrier substrate,the redistribution layer being interposed between the first carriersubstrate and the second carrier substrate. The first carrier substrateis removed to expose an exposed surface of the redistribution layer, andthe exposed surface of the redistribution layer is bonded to asemiconductor structure.

In yet still another embodiment, a method is provided. The methodincludes forming a first passivation layer over a first carriersubstrate, forming redistribution layer over the first passivationlayer, the redistribution layer including one or more metal layersdisposed in one or more second passivation layers, and attaching theredistribution layer to a second carrier substrate. The method furtherincludes removing the first carrier substrate from the first passivationlayer, forming openings in the first passivation layer to exposeportions of a first metal layer of the one or more metal layers, andforming first conductive structures in the openings in the firstpassivation layer, the first conductive structures being electricallycoupled to the first metal layer. The redistribution layer is bonded toa first die package.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: forming a first die packageover a first carrier substrate, the first die package comprising a firstdie and a first electrical connector; forming redistribution layer overa second carrier substrate, the redistribution layer comprising one ormore metal layers disposed in one or more passivation layers, theredistribution layer having a first side and a second side opposite thefirst side, the first side facing the second carrier substrate; removingthe second carrier substrate from the redistribution layer to expose afirst passivation layer of the one or more passivation layers on thefirst side of the redistribution layer; forming openings in the firstpassivation layer to expose portions of a first metal layer of the oneor more metal layers; forming a first set of bonding structures in theopenings in the first passivation layer, the first set of bondingstructures being electrically coupled to the first metal layer; afterremoving the second carrier, bonding the first die package to the firstside of the redistribution layer using the first set of bondingstructures to form a first set of bonding joints, at least one of thefirst set of bonding joints being bonded to the first die of the firstdie package and at least another one of the first set of bonding jointsbeing bonded to the first electrical connector; and after bonding thefirst dies package to the first side of the redistribution layer,removing the first carrier substrate.
 2. The method of claim 1, whereinforming a first die package further comprises: forming a firstdielectric layer over the first carrier substrate; forming the firstelectrical connector over the first dielectric layer, the firstelectrical connector extending from a first side of the first dielectriclayer; mounting the first die to the first side of the first dielectriclayer; and encapsulating the first die and the first electricalconnector with a molding material, the first electrical connectorextending through the molding material.
 3. The method of claim 2,further comprising: removing the first die package from the firstcarrier substrate to expose a second side of the first dielectric layer,the second side being opposite the first side; forming openings from thesecond side of the first dielectric layer to expose portions of thefirst die and the first electrical connector; and bonding a secondpackage to the first die package using a first set of conductiveconnectors, the first set of conductive connectors extending through theopenings in the first dielectric layer.
 4. The method of claim 1,wherein the forming the first set of bonding structures in the openingsin the first passivation layer further comprises: forming a micro bump,a solder ball, solder paste, or a combination thereof in the openings inthe first passivation layer.
 5. A method comprising: formingredistribution layer over a first carrier substrate, the redistributionlayer comprising one or more metal layers disposed in one or morepassivation layers; after forming the redistribution layer, formingsolder connections on the redistribution layer; after forming the solderconnections, attaching the redistribution layer to a second carriersubstrate, the redistribution layer being interposed between the firstcarrier substrate and the second carrier substrate; removing the firstcarrier substrate to expose an exposed surface of the redistributionlayer; and bonding the exposed surface of the redistribution layer to asemiconductor structure.
 6. The method of claim 5, wherein thesemiconductor structure comprises a packaged die, the packaged diecomprising an integrated circuit die with molding compound extendingalong sidewalls of the integrated circuit die.
 7. The method of claim 6,further comprising forming through vias extending through the moldingcompound.
 8. The method of claim 5, wherein the bonding forms anintegrated fan-out structure.
 9. The method of claim 5, furthercomprising: forming a first passivation layer over the first carriersubstrate, wherein the redistribution layer is formed on the firstpassivation layer; after removing the first carrier substrate, formingopenings in the first passivation layer to expose portions of a firstmetal layer of the one or more metal layers; and forming a first set ofbonding structures in the openings in the first passivation layer, thefirst set of bonding structures being electrically coupled to the firstmetal layer.
 10. The method of claim 9, wherein the bonding structuresare bonded directly to corresponding contacts on the semiconductorstructure.
 11. The method of claim 5, further comprising forming adielectric layer over a third carrier substrate; placing a semiconductordie on the dielectric layer; encapsulating the semiconductor die,thereby forming the semiconductor structure; and after bonding theexposed surface of the redistribution layer to the semiconductorstructure, removing the third carrier substrate.
 12. The method of claim11, further comprising forming openings in the dielectric layer andforming bump structures in the openings.
 13. The method of claim 5,wherein the redistribution layer is free of being electrically coupledto active devices prior to bonding the redistribution layer to thesemiconductor structure.
 14. A method comprising: forming a firstpassivation layer over a first carrier substrate; forming redistributionlayer over the first passivation layer, the redistribution layercomprising one or more metal layers disposed in one or more secondpassivation layers; attaching the redistribution layer to a secondcarrier substrate; removing the first carrier substrate from the firstpassivation layer; forming openings in the first passivation layer toexpose portions of a first metal layer of the one or more metal layers;forming first conductive structures in the openings in the firstpassivation layer, the first conductive structures being electricallycoupled to the first metal layer; and bonding the redistribution layerto a first die package, wherein after removing the first carrier andprior to bonding the redistribution layer to the first package, theredistribution layer is free of being electrically coupled to activedevices.
 15. The method of claim 14, further comprising forming thefirst die package over a third carrier substrate, the first die packagecomprising a first integrated circuit die, a first electrical connector,and an encapsulant between the first integrated circuit die and thefirst electrical connector.
 16. The method of claim 15, wherein bondingthe redistribution layer to the first die package comprises directlybonding the first electrical connector to the first conductivestructures.
 17. The method of claim 15, further comprising, afterbonding the redistribution layer to the first die package, removing thethird carrier substrate.
 18. The method of claim 14, further comprising:forming a dielectric layer on a third carrier substrate; forming thefirst die package on the dielectric layer; after bonding the first diepackage to the redistribution layer, removing the third carriersubstrate; and after removing the third carrier substrate, formingelectrical connections on the first die package, the electricalconnections extending through the dielectric layer, the first diepackage being interposed between the electrical connections and theredistribution layer.
 19. The method of claim 14, wherein a conductivestructure of the redistribution layer is directly bonded to a conductivestructure of the first die package.
 20. The method of claim 14, whereina conductive structure of the redistribution layer is solder bonded to aconductive structure of the first die package.